The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The HDA includes at least one disk (such as a magnetic disk, magneto-optical disk, or optical disk), a spindle motor for rotating the disk, and a head stack assembly (HSA). The PCBA includes electronics and firmware for controlling the rotation of the spindle motor and for controlling the position of the HSA, and for providing a data transfer channel between the disk drive and its host.
The spindle motor typically includes a rotor including one or more rotor magnets and a rotating hub on which disks are mounted and clamped, and a stator. If more than one disk is mounted on the hub, the disks are typically separated by spacer rings that are mounted on the hub between the disks. Various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the rotor magnet(s), thereby rotating the hub. Rotation of the spindle motor hub results in rotation of the mounted disks.
The HSA typically includes an actuator, at least one head gimbal assembly (HGA), and a flex cable assembly. During operation of the disk drive, the actuator must rotate to position the HGAs adjacent desired information tracks on the disk. The actuator includes a pivot-bearing cartridge to facilitate such rotational positioning. The pivot-bearing cartridge fits into a bore in the body of the actuator. One or more actuator arms extend from the actuator body. An actuator coil is supported by the actuator body, and is disposed opposite the actuator arms. The actuator coil is configured to interact with one or more fixed magnets in the HDA, to form a voice coil motor. The PCBA provides and controls an electrical current that passes through the actuator coil and results in a torque being applied to the actuator.
Each HGA includes a head for reading and writing data from and to the disk. In magnetic recording applications, the head typically includes a slider and a magnetic transducer that comprises a writer and a read element. In optical recording applications, the head may include a mirror and an objective lens for focusing laser light on to an adjacent disk surface. The slider is separated from the disk by a gas lubrication film that is typically referred to as an “air bearing.” The term “air bearing” is common because typically the lubricant gas is simply air. However, air bearing sliders have been designed for use in disk drive enclosures that contain an alternative gas (e.g. nitrogen) that may not degrade lubricants and protective carbon films as quickly as does a gas like air that contains oxygen.
Disk drive enclosures disclosed in the art to contain an alternative gas are typically hermetically sealed to prevent an unacceptable rate of leakage that might undesirably alter the tribochemistry of the head disk interface, possibly leading to degradation in reliability, head crashes, and associated data loss. Hermetically sealing a disk drive may also beneficially prevent large changes in moisture and humidity within the disk drive.
Various methods and structures that have been disclosed in the past to hermetically seal disk drive enclosures. The evaluation and further improvement of such methods and structures depends, in part, on practical and sensitive leakage testing. However, conventional methods to test for leakage from a hermetically sealed disk drive have required the addition of components and cost to the disk drive devices, and/or have not been sensitive enough to quickly and reliably identify slow or minor leaks that still might ultimately reduce disk drive lifespan months or years later.
Thus, there is a need in the art for an improved method to test for leakage of a hermetically sealed disk drive enclosure, which may be practically implemented and integrated in a high volume and low cost disk drive manufacturing process, and which is sensitive enough to ensure adequate post-manufacture product reliability and lifetime.